- Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements (including St John's Wort, kava, ephedra [ma huang], gingko biloba, DHEA, vohimbe, saw palmetto, ginseng, red yeast rice) within 7 days (or 14 days if the drug is a potential enzyme inducer) or 5 half-lives (whichever is longer) prior to the first dose of study medication and is unwilling to abstain from use of these medications until the last pharmacokinetic or pharmacodynamic sample has been collected, unless in the opinion of the Investigator and GSK Medical Monitor the medication will not interfere with the study procedures or compromise subject safety.